ComboBox dropdown not showing up at all or missing scrollbars

[MGlolenstine]

I've noticed, that on Windows 7, the ComboBox doesn't open at all when pressed, but it still changes if I press the buttons up and down when selected. On Windows 10 and 11, the ComboBox is missing the scrollbar, which makes it harder to select entries that are outside of the visible dropdown. I can re-open the dropdown after I select an option at the visible boundary and have it scroll that way, but it's not optimal.

It could be due to a rendering hack I found mentioned in one of the issues.

EDIT:
Related to #271 .